System information

ENUM has not taken off. The reasons appear to be mostly political in nature. The
problem stems from the fact that there is no one organization that controls numbering
on the PSTN the way that IANA does for the Internet. Since no one entity has a clear
mandate for managing E.164 numbers globally, the challenge of maintaining an accu-
rate and authoritative database for ENUM has proved elusive.
Some countries in Europe have done a good job of delivering reliable ENUM databases,
but in country code 1 (NANP), which contains multiple countries and therefore mul-
tiple regulatory bodies, the situation has become an illogical mess. This is hardly sur-
prising, since the carriers that control E.164 addressing can’t reasonably be expected
to get enthusiastic about allowing you to bypass their networks. The organizations
responsible for implementing ENUM in North America have tended to work toward
creating a PSTN on the Internet, which could save them money, but not you or I.
This is not at all what is wanted. Why would I want to route VoIP calls from my system
to yours across a network that wants to charge me for the privilege? SIP is designed to
route calls between endpoints, and has no real use for the concept of a carrier.
The advantage of all this is supposed to be that when an ENUM lookup is performed,
a valid SIP URI is returned.
Asterisk and ENUM
Asterisk can perform lookups against ENUM databases using either the ENUMLOOKUP()
function or a combination of the ENUMQUERY() and ENUMRESULT() dialplan functions.
ENUMLOOKUP() only returns a single value back from the lookup, and is useful when you
know there is likely to only be one return value (such as the SIP URI you want the
system to dial), or if you simply want to get the number of records available.
Status of ENUM Around the World
In the NANP (and many other) countries, the official e164.arpa zone has not been
formally implemented, and therefore there is no official place to go to perform ENUM
lookups for NANP numbers.
A list of the statuses of various countries’ implementations of ENUM can be found at
http://enumdata.org/. For those countries fortunate enough to have ENUM in produc-
tion, you can perform ENUM lookups directly to their e164.arpa zones of those coun-
tries fortunate enough to have ENUM in production.
For countries without e164.arpa zones, there are several alternative places to perform
lookups, the most popular currently being http://www.e164.org. Note that these or-
ganizations have no formal mandate to maintain the zones they represent. They are
community-based, best-effort projects, and the data contained in them will frequently
be out-of-date.
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